ABSTRACT Emergency Departments (EDs) care for 19 million adolescents each year, the majority of whom are low-income, racial and ethnic minorities, and participating in risky sexual behaviors. Despite a growing interest in expanding the role of the ED to provide preventive care, ED providers identify limited resources and time constraints as barriers to the implementation of public health interventions. Novel interventions are needed that fit efficiently within the ED workflow. Our prior work highlighted a significant public health problem?high risk sex among the adolescent male ED population. We demonstrated that adolescent male ED patients are frequently having sex without condoms, increasing their risk of unintended early fatherhood and sexually transmitted infections (STI). They admit to low knowledge of effective contraceptive methods and having few discussions with medical providers and sexual partners about these methods. However, these male adolescents are receptive to sexual and reproductive health (SRH) interventions, particularly during the ED visit and via digital technology. They are particularly interested in interventions that feel relatable and are from a trustworthy source. To date, no intervention has successfully increased contraceptive use among this high risk, hard-to-reach ED population. Additionally, although evidence suggests that SRH digital interventions can improve SRH health, few interventions specifically target males. To improve adolescent SRH outcomes, we have gathered an accomplished team with expertise in adolescent health, ED-based clinical trials, mobile health, and user- informed digital interventions. We created a novel prototype of an ED-based, theory-based, user-informed SRH digital intervention that includes a tailored educational app and 3 months of personalized and interactive text messaging. The objective of this proposal is to complete rigorous development of the intervention and perform an initial ED evaluation. In Aim #1, we will conduct usability testing and finalize development of the adolescent male-focused SRH digital intervention (entitled ERIC?Emergency Room Interventions to improve Care). In Aim #2, we will conduct a pilot randomized controlled trial of ERIC to assess implementation outcomes and potential effectiveness. We hypothesize that the ERIC intervention will be feasible in the ED setting, be acceptable to adolescent males, demonstrate fidelity, and be adopted by users. We also hypothesize that sexually active adolescent male ED patients who receive ERIC will more often have consistent condom use than those who receive standard outpatient referral alone. These data will inform a subsequent multi-center clinical trial with sufficient power to measure clinically significant changes in consistent condom use. Ultimately, a digital ED- based intervention that is effective and automated can be utilized by other EDs as a reproducible and scalable means to promote sexual and reproductive preventive care, decrease unintended early fatherhood and STI risk among adolescent males, and improve adolescent health outcomes throughout the United States.